1. Field of the Invention
The present invention relates to film cartridge assemblies for use with cameras and, more specifically, to a film cartridge assembly including an improved pressure plate configuration for locating an exposure area of the film in an exposure plane.
2. Description of the Prior Art
It is commonplace to enclose photographic film in a cartridge, cassette, magazine, or the like, designed to afford convenient loading of a camera. Such enclosures typically have been configured to accommodate an elongated strip of roll film. It is also known to provide a plurality of exposure areas in a generally circular array on a disk-shaped sheet of film and to rotate such film disk incrementally to bring successive exposure areas into alignment with the camera's optical axis for exposure. An illustrative example of a film disk arrangement is shown in commonly-assigned U.S. Pat. No. 4,194,822 issued Mar. 25, 1980 to G. S. Sethi.
In the aforementioned patent, a film disk is mounted on a central core to form a film unit adapted to be rotatably supported within a protective casing for insertion into a camera. The protective casing is formed of a rigid material to protect the film from reasonably expected rough handling. An exposure window in the front wall of the casing provides access to the film for a camera's film support surface. The film is urged against the camera's film support surface by a spring biased pressure platen in the camera which acts through an opening in the rear wall of the casing. The opening is covered by an opaque flexible membrane to prevent light and dirt from entering the casing through the opening.
In order for the film to be held firmly against the camera's film support surface, the pressure platen in the camera should be accurately formed and have a high degree of flatness, and the flexible membrane should be exceedingly compliant to faithfully transmit the pressure platen's force and shape to the film to uniformly press the film against the camera's film support surface. Film cartridge assemblies in accordance with the present invention more reliably and accurately locate the film against the camera's film support surface by means of a rigid pressure plate retained by the rear wall of the cartridge. The pressure plate is movable relative to the rear wall to press the film firmly and uniformly against the camera's film support surface without a flexible membrane therebetween.
Although rigid pressure plates in cartridges are also known in the art, such as shown in German Offenlegungsschrift 2,809,856, light integrity of such known cartridges is maintained by interconnecting the rigid pressure plate and the cartridge rear wall by an annular opaque membrane which permits movement of the pressure platen relative to the cartridge walls. The use of a membrane is effective in light-sealing the cartridge opening, but requires a major amount of assembly operation during cartridge manufacture.